The present invention relates to semi-crystalline polymer compositions plasticized with aromatic sulphonamides in which the nitrogen atom contains a substituent carrying a hydroxyl or oxycarbonyl group.
The problem of plasticizers in polymers is well known in the state of the art. Reference may be made, on this subject, to the work xe2x80x9cEncyclopedia of Polymer Science and Engineeringxe2x80x9d, published by Wiley, 1989, Supplement Vol., pp. 568-647, for example, or alternatively to the book xe2x80x9cThe Technology of Plasticizersxe2x80x9d, J. K. Sears and J. R. Darby, John Wiley and Sons Inc., 1982.
It is well known that semi-crystalline polymers, such as polyamide-6, polyamide-6,6, polyamides-4,6, -6,10 and -6,12 and some polyketones, are very difficult to plasticize because of their high melting temperature and of the low compatibility between these polymers and the plasticizers known in the state of the art. This is because, if it is desired to incorporate a plasticizer above these high melting temperatures, typically from 250 to 300xc2x0 C., and even 340xc2x0 C. for polyamide-4,6, the plasticizer rapidly degrades, colouring the polymer, and its destruction does not make it possible to effectively plasticize the polymer; in addition, the plasticizer can also evaporate. Such is the case if attempts are made to use, as plasticizer for these polyamides, N-n-butylbenzenesulphonamide or N-ethyl-p-toluenesulphonamide, for example, plasticizers widely used on an industrial scale to plasticize polyamides with lower melting temperatures. One way of alleviating these disadvantages is to process the polymer so that the plasticizer is only found at a high temperature for the shortest possible time but this way of operating causes great technical difficulties, including very high losses of the plasticizer, problems of air pollution related to the sudden evaporation and/or thermal degradation of the plasticizer, and the like.
In addition to the criterion of good thermal stability which must be exhibited by plasticizers for semi-crystalline polymers with high melting temperatures, there is also the problem of the possible migration from the polymer of these plasticizers with time.
As regards semi-crystalline polymers which have lower melting temperatures, such as polyamide-11, polyamide-12, polyoxymethylene or poly(vinylidene fluoride), for which polymers a plasticizer is incorporated at temperatures of the order of 220xc2x0 C., the problem of the thermal stability of the plasticizer is less critical. However, the intrinsic volatility of a plasticizer such as N-n-butylbenzenesulphonamide can be the source of problems, such as a loss of the product, and smells, which will have to be eliminated by means of complex and expensive equipment.
It would therefore be advantageous to find plasticizers for semi-crystalline polymers with high melting temperatures, such as polyamide-6, polyamide-6,6, polyamides-4,6, -6,9, -6,10, -6,12 and MXD-6 and some polyketones, but also polyamide-11, polyamide-12, polyoxymethylene and poly(vinylidene fluoride), which would be stable at high temperatures ranging from 220 to 300xc2x0 C. and even 340xc2x0 C. for polyamide-4,6 without undergoing either consequent decomposition or consequent evaporation. These plasticizers should not migrate towards the surface of the polymer either, in order to avoid the problem of exudation. In addition, it goes without saying that these plasticizers should effectively exhibit plasticizing properties at least equivalent to and preferably better than those of the plasticizers known in the state of the art.
The Applicant Company has now found, surprisingly, a family of aromatic sulphonamides in which the nitrogen atom contains a substituent carrying a hydroxyl or oxycarbonyl group which fully meets all the requirements mentioned above for plasticizers for semi-crystalline polymers with a high melting temperature and a processing temperature equal to or greater than 220xc2x0 C., preferably 250xc2x0 C.
For this reason, the present invention relates to compositions comprising at least one polymer and at least one plasticizer, characterized in that
a. the polymer is semi-crystalline and exhibits a processing temperature equal to or greater than 220xc2x0 C., preferably 250xc2x0 C.,
b. the plasticizer is an aromatic benzenesulphonamide represented by the general formula (I) 
in which
R1 represents a hydrogen atom, a C1-C4 alkyl group or a C1-C4 alkoxy group,
X represents a linear or branched C2-C10 alkylene group, or
a cycloaliphatic group, or
an aromatic group,
Y represents one of the groups OH or 
R2 representing a C1-C4 alkyl group or an aromatic group, these groups optionally themselves being substituted by an OH or C1-C4 alkyl group.
The preferred aromatic benzenesulphonamides of formula (I) are those in which:
R1 represents a hydrogen atom or a methyl or methoxy group,
X represents a linear or branched C2-C10 alkylene group or a phenyl group,
Y represents an OH or xe2x80x94Oxe2x80x94COxe2x80x94R2 group,
R2 representing a methyl or phenyl group, the latter being themselves optionally substituted by an OH or methyl group.
The semi-crystalline polymers to which the present invention relates are those for which the processing temperature is equal to or greater than 220xc2x0 C., preferably 250xc2x0 C., this processing temperature being imposed by the high melting temperature of these polymers. Mention may be made, among these, of polyamide-6, polyamide-6,6 and some polyketones, on account of the plasticization problems which they pose by virtue of their high melting temperature. The polyketones concerned here are condensation products of carbon monoxide with aliphatic olefins, for example the condensation product of carbon monoxide with ethene and propene. These polyketones are well known in the state of the art (mention may be made, without implied limitation, of Patents EP 485,058, EP 213,671 and EP 121,965, for example). The present invention also relates to polyamides-4,6, -6,9, -6,10, -6,12 and MDX-6. Other semi-crystalline polymers, such as polyamide-11, polyamide-12, polyoxymethylene and poly(vinylidene fluoride), can also be advantageously plasticized by the aromatic sulphonamides of formula (I).
Mention may be made, among the aromatic sulphonamides of formula (I) which are liquid (L) or solid (S) at room temperature as specified below, of the following products, with the abbreviations which have been assigned to them:
AS: N-(2-hydroxyethyl)benzenesulphonamide
C6H5SO2NH(CH2)2OH (L)
AY: N-(3-hydroxypropyl)benzenesulphonamide
C6H5SO2NH(CH2)3OH (L)
BC: N-(2 -hydroxyethyl)-p-toluenesulphonamide
CH3C6H4SO2NH(CH2)2OH (S)
BE: N-(4-hydroxyphenyl)benzenesulphonamide
C6H5SO2NHC6H4OH (S)
BF: N-[(2-hydroxy-1-hydroxymethyl-1-methyl)ethyl]-benzenesulphonamide
C6H5SO2NHC(CH3)(CH2OH)CH2OH (L)
BG: N-[5-hydroxy-1,5-dimethylhexyl]benzenesulphonamide
C6H5SO2NHCH(CH3)(CH2)3C(CH3)2OH (S)
BH: N-(2-acetoxyethyl)benzenesulphonamide
C6H5SO2NH(CH2)2OCOCH3 (S)
BI: N-(5-hydroxypentyl)benzenesulphonamide
C6H5SO2NH(CH2)5OH (L)
BK: N-[2-(4-hydroxybenzoyloxy)ethyl]benzene-sulphonamide
C6H5SO2NH(CH2)2OCOC6H4OH (S)
BL: N-[2-(4-methylbenzoyloxy)ethyl]benzenesulphonamide
C6H5SO2NH(CH2)2OCOC6H4CH3 (S)
BJ: N-(2-hydroxyethyl)-p-methoxybenzenesulphonamide
CH3OC6H4SO2NH(CH2)2OH (S)
BM: N-(2-hydroxypropyl)benzenesulphonamide
C6H5SO2NHCH2CH(CH3)OH (L)
The advantages introduced by the aromatic sulphonamides of formula (I) in the plasticization of the semi-crystalline polymers are many. Among these, mention may be made of:
the high thermal stability of the sulphonamides makes it possible to incorporate them in polymers at high temperature without them substantially evaporating, which prevents losses of the product and atmospheric pollution; they do not decompose at high temperature, which prevents unacceptable colouring of the polymer and allows them to act as plasticizer since they remain present intact in the polymer. It is consequently possible henceforth to use these new plasticizers for processing techniques (injection moulding, extrusion, extrusion blow-moulding, rotational moulding, and the like) at high temperatures and with contact times such that the plasticizers known in the state of the art cannot be used because of their volatility and/or their degradation at these temperatures,
their high compatibility with the abovementioned polymers also promotes the development of their plasticizing properties,
their plasticizing effect is reflected by a large decrease in the mechanical torque developed by the molten medium during mixing of the plasticizer with the polymer as well as during any processing of these compositions, which represents a large decrease in the energy to be used during these operations; the plasticizing effect is also reflected by a fall in the glass transition temperature, which results in a decrease in the stiffness of the articles obtained starting with these compositions, which can be measured by the fall in the elastic modulus, determined by the tensile test (ISO Standard 527-1 and 527-2), and by an improvement in the impact strength (measurable, for example, by the test known under the name of xe2x80x9cNotched Izod impactxe2x80x9d according to ISO Standard 180).
Some aromatic sulphonamides corresponding to the formula (I) have already been used as polymer plasticizers.
U.S. Pat. No. 3,748,296 describes aromatic sulphonamides mono- or disubstituted on the nitrogen atom by alkyl groups which can themselves be substituted by a hydroxyl, alkoxy or acyloxy group. These products are used, as plasticizers, solely for polyurethanes.
U.S. Pat. No. 2,201,028 also describes aromatic sulphonamides mono- or disubstituted on the nitrogen atom by alkyl groups carrying hydroxyl groups. These compounds are used, as plasticizers, solely for urea-formaldehyde resins, alone or as a mixture with cellulose polymers.
Patent GB 455,694 also describes aromatic sulphonamides mono- or disubstituted on the nitrogen atom by alkyl groups carrying ester or hydroxyl groups as plasticizers solely for ethers and cellulose ethers. The article by D. Aelony in Ind. Engineer. Chem., 46, pp. 587-591 (1954) describes esters of the same type as those in Patent GB 455,694 as plasticizers for vinyl resins alone.
U.S. Pat. No. 2,292,464 provides N-hydroxyalkyl-N-(aryl)arylsulphonamides as plasticizers for various polymers, essentially for cellulose derivatives; polyamides are mentioned among these polymers, without further details. In practice, the sulphonamides disubstituted on the nitrogen atom of this patent have plasticizing properties markedly inferior to those of aromatic sulphonamides monosubstituted on the nitrogen atom of formula (I) for semi-crystalline polymers with high melting temperatures according to the present invention.
Finally, Patent Application JP 2-221467 describes adhesives for textile pieces composed of a mixture of an N-hydroxyalkylated benzenesulphonamide and of a heat-meltable resin containing a polyamide; these adhesives can be used at 130xc2x0 C.
As is well known to the person skilled in the art, it is impossible to predict what will be the properties of a compound which is a good plasticizer for a given polymer when attempts are made to use it as plasticizer for a polymer of a very different nature. Moreover, none of the abovementioned documents tackles the question of the plasticization of semi-crystalline polymers which can only be processed at high temperatures or explains the problems which this causes, no more than the solutions to be introduced thereto.
Aromatic sulphonamides other than those of formula (I) have already been provided as plasticizers for polyamides with high melting temperatures, such as polyamides-6, -6,6, and the like. Thus it is that, in U.S. Pat. No. 2,499,932, the reaction products of alcohols with N-alkylolarylsulphonamides are provided as plasticizers for these polyamides. These reaction products would be ethers of N-alkylolarylsulphonamides, but condensation reactions during the synthesis of these products could give rise to more complex molecules than a simple ether; the examples given of these products are all C1-C8 alkyl ethers of N-methyloltoluenesulphonamide. In fact, the thermal stability of this type of compound is much poorer than that of the aromatic sulphonamides of formula (I), as can be seen in Example 2 below. U.S. Pat. No. 2,244,183 provides, as plasticizer for the same polyamides, resins resulting from the condensation of formaldehyde with toluene- or cyclohexanesulphonamides optionally substituted by an alkyl group on the nitrogen atom. These resins have a much poorer plasticizing effect than the aromatic sulphonamides of formula (I).
The aromatic sulphonamides of formula (I) can be synthesized conventionally by reacting benzenesulphonyl chloride, optionally substituted on the benzene ring by an R1 group according to the formula (I), with an amine of formula NH2xe2x80x94Xxe2x80x94Y, in which X has the meaning given above and Y represents a hydroxyl group, with heating in water or in an inert solvent, such as benzene or toluene, in the presence of a base, such as sodium hydroxide, pyridine or the amine NH2xe2x80x94Xxe2x80x94Y in excess; the benzenesulphonyl chloride is preferably added dropwise to the amine in aqueous or organic solution, care being taken that the pH does not fall below the value 9. When Y represents an xe2x80x94Oxe2x80x94COxe2x80x94R2 group, R2 having the meaning given above, a hydroxylated benzene-sulphonamide obtained as described above is esterified with the carboxylic acid or the anhydride corresponding to this Y group, optionally under catalytic conditions. Many examples of this type of synthesis are given in the literature, for example in the abovementioned article by D. Aelony.
The finished product is isolated according to the techniques well known to the person skilled in the art, for example by extraction with a third solvent chosen from aromatic or cycloaliphatic hydrocarbons, aliphatic esters or ketones or alternatively chlorinated solvents, such as chloroform. The isolation technique will depend on the solubility of the product synthesized.
The amount of the aromatic sulphonamide of formula (I) used according to the present invention depends on the polymer concerned and on its industrial application and most often varies from 2% to 30% and preferably from 5% to 20% by weight with respect to the total weight of the composition.
Various techniques can be used for introducing the aromatic sulphonamide of formula (I) into the semi-crystalline polymer according to the present invention. The most usual technique consists in mixing the plasticizer and the polymer in the molten state. The most widely used method industrially for doing this is extrusion. An aromatic sulphonamide of formula (I) existing in the liquid form at room temperature will be appropriately introduced via a metering pump in the feed zone of the extruder simultaneously with the polymer granules, the throughput of the metering pump being adjusted so as to provide a rod of the desired composition at the extruder outlet. If the aromatic sulphonamide of formula (I) exists in the solid form at room temperature, the polymer granules will be dry-mixed beforehand with the appropriate amount of the abovementioned product. The polymer granules, thus coated with plasticizer, will then be introduced into the feed zone of the extruder. For aromatic sulphonamides with low melting points, it is possible to feed the extruder with plasticizer in the molten state (liquid) via a pump equipped for this purpose. On a laboratory scale, use will conveniently be made of a thermostatically-controlled kneader in which rotate steel knives which homogenize the composition in the molten state, the polymer granules and the plasticizer having been dry-mixed beforehand.
It is also possible to introduce the sulphonamide of formula (I) into the semi-crystalline polymer by dissolving these products in a solvent or a mixture of solvents. This technique can advantageously be used for the preparation of samples in the form of films, for analytical purposes, for example.
Finally, it is also possible to obtain the compositions according to the invention by introducing the sulphonamide of formula (I) into the reactor in which the polymer is synthesized, either at the beginning of this synthesis or during or at the end of the latter.
The compositions according to the invention can additionally comprise additives usual for semi-crystalline polymers, such as impact reinforcements, inorganic fillers, antioxidants, UV stabilizers, processing aids, such as mould-release agents, and the like.
The compositions according to the invention lend themselves to the manufacture of finished components obtained by processes, such as extrusion and injection moulding, in which the plasticized polymer is processed in the molten state. Mention may be made, among the articles thus manufactured, of hydraulic brake cables, pipes, tubes, tanks and other engineering components.
On account of the excellent plasticization of the polymers targeted by the present invention, it is now possible to envisage the use of these in the same applications under easy processing conditions, which was not possible previously.
The examples which follow illustrate the invention without limiting it.